A composite sheet material with a synthetic resin impregnated in a glass fiber sheet material is universally applied as a blank of various industrial products. Such composite sheet material is available in the forms of prepreg material wherein an impregnation resin is retained as uncured and cure material wherein an impregnation resin is fully cured. However, it has never been made in a prior art that a single composite sheet material is provided with surfaces one of which is retained as uncured and other of which is fully cured.
Though it is easy to apply a deformation processing to the prepreg material, the material may not readily accept an automatic punching or mold releasing operations. In turn, though it is easy to punch or release the cure material from a mold, the material may not readily accept a deformation processing and tends to resume its original shape after processed.
Therefore, an extreme industrial benefit will be derived if a composite sheet material possessing advantageous characteristics of above two materials in combination is available to use.